(1) Field of the Invention
This invention relates to novel phosphoric esters and more particularly, to phosphoric esters of the following general formula (I) ##STR3## in which R.sup.1 represents a linear or branched alkyl or alkenyl group having from 1 to 36 carbon atoms, in which hydrogen atoms are optionally replaced by fluorine atoms, or a phenyl group substituted with a linear or branched alkyl group having from 1 to 15 carbon atoms, R.sup.2 represents an alkylene group having 2 or 3 carbon atoms, n is a value of from 0 to 30, and M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium, an alkylamine or an alkanol amine. The invention also relates to a process for preparing the phosphoric esters.
(2) Description of the Prior Art
Phospholipids are amphiphilic compounds having both a hydrophobic moiety and a hydrophilic moiety in the molecule thereof and are utilized, as biosurfactants, in wide fields of cosmetics, foods and medicines by making use of their emulsifying, dispersing, foaming and moisture-retaining functions. The phospholipids in vivo are constituent components of cell membranes and have various functions of cell partition and sectional formation, and transport of substances. In recent years, it has been clarified that they play an important role in various biological activities.
The phospholipids have, in most cases, such a phosphoric diester structure that the hydrophobic and hydrophilic moieties are joined through a phosphoric ester bond. Moreover, the hydrophilic moiety has a complicated structure such as a betaine structure having a phosphoric acid group and an amino group or an amino acid group, or a structure having a phosphoric acid group, a charge-free glycerine group and a sugar group. The properties of a phospholipid depend on the structure of the hydrophilic moiety.
Accordingly, if phospholipids or analogues thereof could be chemically prepared, they would be applicable not only to cosmetics and medicines, but also to a wide variety of other general industrial products. A number of attempts have been made to chemically prepare phosphlipids or analogous compounds thereof. Most of them require multi-step reactions, so that intended products can be obtained only in low yield and thus, the industrial production was not successful [e.g. Bear et al, J. Amer. Chem. Soc., 72, 942, (1950)]. Accordingly, there is a demand for the preparation of phospholipid analogue compounds in an industrial and simple manner. Moreover, if precursors which permit easy introduction of, for example, an amino group and an amino acid group other than a phosphoric acid group of the hydrophilic moiety could be industrially prepared, preparation of various types of phospholipid analogue compound would become possible.
On the other hand, many studies have been made in the field of polymers in order to impart the properties of a phosphorous moiety to polymer compounds. More particularly, polymerization of polymerizable group-bearing phosphorus-containing compounds as monomers and modification of polymeric compounds with phosphorus-containing compound have been extensively studied.
It has been made clear that a cell membrane has a bimolecular phospholipid membrane (which is oriented in a good order owing to physical properties of phospholipid molecules, or a self-organizing tendency inherent to an amphiphilic compound having both hydrophobic and hydrophilic groups in which the molecules gather and set up by themselves). Studies have been made to artificially prepare the bilayer film vesicle (liposome) and apply it as a model of a biomembrane or as a microcapsule. Further, the bimolecular membrane structure is converted into a macromolecule, i.e. a phospholipid analogue compound having a polymerizable hydrophobic or hydrophilic group is prepared. For instance, Regen et al prepared a compound of the following formula (III) [J. Amer. Chem. Soc., 105, 2975 (1983)]. ##STR4##
However, the preparation of these substances requires multi-step reaction steps, making the industrial production difficult.
The glycidyl group is a functional group which is not only polymerizable, but also highly reactive with various groups such as, for example, an amino group, a carboxyl group and the like, to give adducts. If the glycidyl group can be introduced into the phosphoric acid group, the resultant product serves not only as a phosphorus compound for monomer, but also as a modifying agent for polymers. Moreover, if the phosphorus compound having the glycidyl group has such an amphiphilic structure as phospholipids, i.e. if it has a glycidyl group aside from a structure having a hydrophobic group and a phosphoric acid group serving as a hydrophilic groups, it may be converted to a precursor which is important in preparing a phospholipid analogue compound as set forth before, or may be used as a polymerizable group-bearing phospholipid analogue compound or as a precursor thereof.
However, only a few phosphoric esters having a glycidyl group are known up to now, including compounds in which 2 moles of glycidyl groups are joined to a phosphoric monoester, e.g. compounds of the following formula (IV) prepared by Rizpolozhenskii et al [Izv. Akad. Nauk SSSR, Ser. Khim., (9), 2006(1967)] ##STR5## in which Ph represents a phenyl group; and compounds in which 1 mole of a glycidyl group is joined to a phosphoric diester, e.g. compounds of the following formula (V) prepared by Mularczyk et al [Tenside Detergents, 21, #4, 194(1984)] ##STR6## These compounds are free of a phosphoric acid group acting as a hydrophilic group. The above compounds, therefore, cannot be a precursor for phospholipid analogue compounds since they do not have all the moieties as described before, that is, a hydrophobic group, a phosphoric acid group as a hydrophilic group and a glycidyl group.